1. Field of the Invention
This invention relates to acid-functional polymers obtained by the ring opening half-ester reaction, or the hydrolysis, of specified anhydride-functional polymers. The anhydride-functional polymers which are used to prepare the acid-functional polymers are obtained by at least partially hydrogenating an unsaturated polymer which was, in turn, obtained by reacting, under ene reaction conditions, (i) an unsaturated anhydride having the structure: ##STR2## wherein R.sub.1 and R.sub.2 are each independently hydrogen, alkyl of 1 to about 6 carbons, or alkoxy of 1 to about 6 carbons, or a halogen; and (ii) at least one polyolefin having at least two carbon-carbon double bonds in the polyolefin backbone and having an average of at least three carbon atoms in the polyolefin backbone between the carbon-carbon double bonds.
The polyolefin which is reacted under ene reaction conditions with the unsaturated anhydride will have an average of at least three carbon atoms in the backbone between the carbon-carbon double bonds. The backbone of such a polyolefin would be comprised primarily of repeating units having the structure: EQU --[--(CR.sub.3 R.sub.4).sub.x --CHR.sub.5 --CH.dbd.CH--]--
wherein each x is individually a number from 2 to about 15; and R.sub.3, R.sub.4 and R.sub.5 are each individually hydrogen, or a linear, branched or cyclic aliphatic group of 1 to about 18 carbon atoms. By "primarily" is meant that at least 60% by weight, and preferably at least 90% by weight, of the repeating backbone units of the polyolefin would have that structure.
The preferred polyolefin has the structure: EQU Z--CH.dbd.CH--[--(CR.sub.3 R.sub.4).sub.x --CHR.sub.5 --CH.dbd.CH--].sub.n --Z
wherein each x, R.sub.3, R.sub.4 and R.sub.5 is as defined above; each Z is individually hydrogen, or a linear, branched, or cyclic aliphatic group of 1 to about 36 carbons; and n is a number between 2 and 5,000.
Between 1% and 100%, and preferably between 20% and 95% of the carbon-carbon double bonds of the unsaturated polymer obtained by the ene reaction will be hydrogenated to produce the hydrogenated anhydride-functional polymers which are subsequently converted to the acid-functional polymers. The hydrogenated anhydride-functional polymers should have an average of at least two anhydride groups per molecule. As used herein, the term "hydrogenated anhydride-functional polymer" means a polymer in which at least 1% of the carbon-carbon double bonds have been hydrogenated.
The acid-functional polymers obtained from the hydrogenated anhydride-functional polymers should have an average of at least two carboxylic acid groups per molecule and are useful as corrosion or scale inhibitors, thickeners, dispersants and as reactive agents and/or crosslinking agents for compounds having an average per molecule of at least two functional groups, such as epoxy, hydroxyl or amine groups, which are reactive with acid groups. The acid-functional polymers can, therefore, be utilized in a variety of materials such as plastics, fibers, adhesives, paper sizing, inks and, particularly, coating compositions.
This invention also relates to novel reactive compositions which utilize the acid-functional polymer in combination with one or more other materials which can react with acid groups. These reactive compositions can be reacted at room temperature or force dried at temperatures ranging up to about 350.degree. F. or higher if desired. When utilized as reactive crosslinking agents for coatings, the acid-functional polymers may be utilized in a variety of coating applications, including primers and topcoats as well as clearcoats and/or basecoats in clearcoat/basecoat compositions.
The reactive compositions typically involve the combination of the acid-functional polymer with an epoxy-functional compound. The reactive composition may, optionally, also incorporate an anhydride-functional compound and, optionally, also a hydroxyl-functional compound. All of these combinations can provide fast reacting, durable coatings which minimize the toxicity problems which may be associated with other low temperature curing systems.
2. Description of the Prior Art
Unsaturated, polymerizable acids, such as maleic acid, acrylic acid, methacrylic acid and polymers or copolymers incorporating these materials are known in the art. By the selection of one or more of these acids, polymers may be tailored to provide a desired acid value, reactivity or other desired property. The prior art has not, however, taught polymers obtained by the half-ester reaction or the hydrolysis of the anhydride-functional polymers taught herein.
Coating compositions comprising reactive combinations of epoxy-containing compounds and compounds having acid functionality are known in the art. For example, U.S. Pat. No. 4, 107, 114 teaches the ene reaction of maleic anhydride and unsaturated polyolefins such as polypentadiene. The resultant anhydride-functional polymer can be subjected to a ring cleavage reaction to produce an acid-functional polymer. Additionally, U.S. Pat. No. 4,859,758 teaches an acid-functional cellulose ester based polymer which could be used in combination with a polyepoxide, and optionally, a polyanhydride and, optionally a hydroxy-functional compound. Similarly, coating compositions comprising cyclic anhydrides and hydroxy-functional compounds are also known in the art. The prior art has not, however, taught the novel acid-functional polymers of this invention nor has it taught coating compositions comprising these acid-functional polymers with epoxy-functional compounds and, optionally, anhydride-functional compounds, and, optionally, hydroxy-functional compounds to provide low temperature curing coatings having excellent durability and performance.